Beamforming generation method in system for simultaneously transmitting wireless information and power, and recording medium and apparatus for performing same

ABSTRACT

A beamforming method in a simultaneous wireless information and power transfer system and an apparatus therefor may derive a transmission signal transmitted to a plurality of information users and a plurality of energy users from a base station having an N T  (here, N T  is a natural number) number of antennas included in each cell, derive a SINR (Signal to Interference plus Noise Ratio) of an i th  (here, i is a natural number) information user by using a noise power of the i th  (here, i is a natural number) information user included in a m th  (here, m is a natural number) cell, derive a harvested power of a j th  (here, j is a natural number) energy user included in the m th  (here, m is a natural number) cell, and perform beamforming by using a transmission signal power at the base station and a total harvested power of the plurality of energy users receiving a transmission signal from the base station. Accordingly, it is possible to improve the effect of minimizing the transmission power of the base station and maximizing the harvested power of the energy users while satisfying the QoS (Quality of Service) and transmission power limitation of the information users.

TECHNICAL FIELD

This disclosure relates to a beamforming method in a simultaneouswireless information and power transfer system, and a recording mediumand an apparatus therefor, and more particularly, to a beamformingmethod in a simultaneous wireless information and power transfer system,which may perform efficient beamforming in a wireless communicationnetwork environment where a transmitter and a receiver exchange RF(Radio Frequency) signals, and a recording medium and an apparatustherefor.

BACKGROUND ART

Recently, attempts to apply wireless energy transmission technology inenergy constrained wireless networks are being actively made.

For example, a wireless powered communication network (WPCN) configuredto wirelessly charge user terminals with signals emitted by atransmitter so that the user terminals may transmit information signalsusing the harvested energy is being studied.

Accordingly, experiments on a simultaneous wireless information andpower transfer system to maximize a total harvested energy of energyusers who harvest energy while satisfying QoS (Quality of Service) ofinformation users are also being conducted.

However, in the existing simultaneous wireless information and powertransfer system, there are various problems since optimization is notperformed in consideration of power consumed by a base station, theefficiency of energy users is not considered, and a non-linear model isnot considered.

PRIOR LITERATURES Patent Literature

-   (Patent Literature 1) Korean Unexamined Patent Publication No.    10-2017-0112746-   (Patent Literature 2) Korean Patent Registration No. 10-1887526-   (Patent Literature 3) U.S. Pat. No. 9,408,155 B2-   (Patent Literature 4) Korean Patent Registration No. 10-1697431

Non-Patent Literature

-   (Non-patent Literature 1) MIMO broadcasting for simultaneous    wireless information and power transfer, R. Zhang and C. K. Ho, IEEE    Transactions on Wireless Communications, vol. 12, No. 5, pp.    1989-2001, May 2013.

DISCLOSURE Technical Problem

In an aspect of the present disclosure, there is provided a beamformingmethod in a simultaneous wireless information and power transfer systemin which energy harvesting technology using an RF signal is grafted to acommunication system, and a recording medium and an apparatus therefor.

The technical problem of the present disclosure is not limited to theabove, and other technical problems not mentioned herein will be clearlyunderstood by those skilled in the art from the following description.

Technical Solution

In one general aspect, there is provided a beamforming method in asimultaneous wireless information and power transfer system, comprising:deriving a transmission signal transmitted to a plurality of informationusers and a plurality of energy users from a base station having anN_(T) (here, N_(T) is a natural number) number of antennas included ineach cell; deriving a SINR (Signal to Interference plus Noise Ratio) ofan i^(th) (here, i is a natural number) information user by using anoise power of the i^(th) (here, i is a natural number) information userincluded in a m^(th) (here, m is a natural number) cell; deriving aharvested power of a j^(th) (here, j is a natural number) energy userincluded in the m^(th) (here, m is a natural number) cell; andperforming beamforming by using a transmission signal power at the basestation and a total harvested power of the plurality of energy usersreceiving a transmission signal from the base station.

The harvested power may be derived by deriving a linear harvested powerby applying the j^(th) (here, j is a natural number) energy user to alinear model, deriving a non-linear harvested power by applying thej^(th) (here, j is a natural number) energy user to a non-linear model,and deriving a harvested power for the j^(th) (here, j is a naturalnumber) energy user by using the derived linear and non-linear harvestedpowers.

The linear harvested power may be derived by using a reception signalpower (P_(jm) ^(E)) and a power conversion efficiency (η_(jm)) of thej^(th) (here, j is a natural number) energy user of the m^(th) (here, mis a natural number) cell.

The non-linear harvested power may be derived by using a maximumharvested power (M_(jm)), a charging rate (a_(jm)) and a sensitivity(b_(jm)) of the j^(th) (here, j is a natural number) energy user of them^(th) (here, m is a natural number) cell, which are parameters of thenon-linear model.

The beamforming may be performed by non-linearly optimizing thetransmission signal power of the base station and the total harvestedpower of the energy users based on QoS (Quality of Service) of theinformation users.

In a computer-readable recording medium according to another embodimentof the present disclosure, a computer program for performing thebeamforming method in a simultaneous wireless information and powertransfer system is recorded.

A beamforming apparatus in a simultaneous wireless information and powertransfer system still another embodiment of the present disclosurecomprises a signal deriving unit configured to derive a transmissionsignal transmitted to a plurality of information users and a pluralityof energy users from a base station having an N_(T) (here, N_(T) is anatural number) number of antennas included in each cell; a noisederiving unit configured to derive a SINR of an i^(th) (here, i is anatural number) information user by using a noise power of the i^(th)(here, i is a natural number) information user included in a m^(th)(here, m is a natural number) cell; a harvested power deriving unitconfigured to derive a harvested power of a j^(th) (here, j is a naturalnumber) energy user included in the m^(th) (here, m is a natural number)cell; and a forming unit configured to perform beamforming by using atransmission signal power derived by the signal deriving unit and atotal harvested power of the plurality of energy users derived from theharvested power derived by the harvested power deriving unit.

The harvested power deriving unit may include a first deriving unitconfigured to derive a linear harvested power by applying the j^(th)(here, j is a natural number) energy user to a linear model; a secondderiving unit configured to derive a non-linear harvested power byapplying the j^(th) (here, j is a natural number) energy user to anon-linear model; and a coupling unit configured to derive a harvestedpower for the j^(th) (here, j is a natural number) energy user by usingthe derived linear and non-linear harvested powers.

The first deriving unit may be configured to derive the linear harvestedpower by using a reception signal power (P_(jm) ^(E)) and a powerconversion efficiency (η_(jm)) of the j^(th) (here, j is a naturalnumber) energy user of the m^(th) (here, m is a natural number) cell.

The second deriving unit may be configured to derive the non-linearharvested power by using a maximum harvested power (M_(jm)), a chargingrate (a_(jm)) and a sensitivity (b_(jm)) of the j^(th) (here, j is anatural number) energy user of the m^(th) (here, m is a natural number)cell, which are parameters of the non-linear model.

The forming unit may be configured to non-linearly optimize thetransmission signal power of the base station and the total harvestedpower of the energy users based on QoS (Quality of Service) of theinformation users.

Advantageous Effects

According to an aspect of the present disclosure described above, it ispossible to perform more efficient beamforming by considering a powerconsumed by a base station and deriving a harvested power applied to anon-linear model as well as a linear model.

In addition, the effect of minimizing a transmission power of the basestation and maximizing a harvested power of energy users whilesatisfying the QoS (Quality of Service) and the transmission powerlimitation of information users may be expected.

The effects may be obtained from the present disclosure are not limitedto above, and other effects not mentioned herein will be clearlyunderstood by those skilled in the art from the following description.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a beamforming apparatus in asimultaneous wireless information and power transfer system according toan embodiment of the present disclosure.

FIG. 2 is a block diagram concretely showing a harvested power derivingunit of FIG. 1.

FIG. 3 is a flowchart for schematically illustrating a beamformingmethod in a simultaneous wireless information and power transfer systemaccording to an embodiment of the present disclosure.

FIG. 4 is a flowchart for concretely illustrating a process of derivinga harvested power of FIG. 3.

FIG. 5 is an exemplary diagram showing a simultaneous wirelessinformation and power transfer system to which the beamforming apparatusin a simultaneous wireless information and power transfer systemproposed in the present disclosure is applied.

FIG. 6 is a diagram showing a linear harvested power derived by applyingto a linear model of the beamforming method in a simultaneous wirelessinformation and power transfer system according to the presentdisclosure.

FIG. 7 is a diagram showing a non-linear harvested power derived byapplying to a non-linear model of the beamforming method in asimultaneous wireless information and power transfer system according tothe present disclosure.

BEST MODE

The following detailed description of the present disclosure refer tothe accompanying drawings that exemplarily illustrate specificembodiments in which the present disclosure may be implemented. Theseembodiments are described in sufficient detail to enable a personskilled in the art to practice the present disclosure. It should beunderstood that various embodiments of the present disclosure aredifferent but need not be exclusive from each other. For example,specific shapes, structures and characteristics described herein may beimplemented in other embodiments without departing from the idea andscope of the present disclosure in relation to one embodiment. Inaddition, it should be understood that locations or arrangement ofindividual components in each disclosed embodiment may be changedwithout departing from the idea and scope of the present disclosure.Accordingly, the following description is not intended to limit thescope, and the scope of the present disclosure, if properly described,is limited only by the appended claims, along with all scopes equivalentto the features defined in the claims. Like reference numerals in thedrawings indicate the same or similar functions over several aspects.

Hereinafter, preferred embodiments of the present disclosure will bedescribed in more detail with reference to the drawings.

The present disclosure is directed to a beamforming apparatus in asimultaneous wireless information and power transfer system, which mayperform more efficient beamforming by deriving a harvested power appliedto not only a linear model but also a non-linear model.

FIG. 1 is a block diagram showing a beamforming apparatus in asimultaneous wireless information and power transfer system according toan embodiment of the present disclosure.

A beamforming apparatus 100 in a simultaneous wireless information andpower transfer system according to an embodiment of the presentdisclosure (hereinafter, referred to as a beamforming apparatus) mayinclude a signal deriving unit 110, a noise deriving unit 130, aharvested power deriving unit 150, and a forming unit 170.

The signal deriving unit 110 may derive transmission signals transmittedto a plurality of information users and a plurality of energy users atan m^(th) (here, m is a natural number) base station (BS) having anN_(T) (here, N_(T) is a natural number) number of antennas included ineach cell.

Here, an m (here, m is a natural number) number of cells may beprovided, and the cell may include one base station having an N_(T)(here, N_(T) is a natural number) number of antennas, a plurality ofinformation users, and a plurality of energy users.

The base station may simultaneously transmit information and power tothe plurality of information users and the plurality of energy usershaving a single antenna by using the N_(T) (here, N_(T) is a naturalnumber) number of antennas.

The transmission signal (x_(m)) transmitted at the m^(th) (here, m is anatural number) base station to the information users and the energyusers may be derived through [Equation 1] below.

$\begin{matrix}{x_{m} = {{\sum\limits_{i \in {\mathcal{u}}_{m}^{i}}{w_{im}s_{im}^{I}}} + {\sum\limits_{j \in {\mathcal{u}}_{m}^{E}}{v_{jm}s_{jm}^{E}}}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Here, w_(im) may mean beamforming for an i^(th) information user whoreceives information from the m^(th) base station, and v_(jm) may meanbeamforming for a j^(th) energy user who receives energy from the m^(th)base station.

In addition, s_(im) ^(I) may mean a symbol for the i^(th) informationuser of the m^(th) cell, s_(jm) ^(E) may mean a symbol for the j^(th)energy user of the m^(th) cell, u_(m) ^(I) may mean a group of theplurality of information users of the m^(th) cell, and u_(m) ^(E) maymean a group of the plurality of energy users of the m^(th) cell.

The reception signal (y_(im) ^(I)) received by the i^(th) (here, i is anatural number) information user of the m^(th) (here, m is a naturalnumber) cell may be derived through [Equation 2] below, and thereception signal (y_(jm) ^(E)) received by the j^(th) (here, j is anatural number) information user of the m^(th) (here, m is a naturalnumber) cell may be derived through [Equation 3] below.

$\begin{matrix}{y_{im}^{I} = {\overset{\overset{{desired}\mspace{14mu}{signal}}{︷}}{h_{imm}^{H}w_{im}s_{im}^{I}} + \overset{\overset{{intra}\text{-}{cell}\mspace{14mu}{interference}}{︷}}{\sum\limits_{k \in {{\mathcal{u}}_{m}^{I}\backslash{\{ i\}}}}{h_{imm}^{H}w_{km}s_{km}^{I}}} + \overset{\overset{{inter}\text{-}{cell}\mspace{14mu}{interference}}{︷}}{\sum\limits_{n \in {\mathcal{M}\backslash{\{ m\}}}}{\sum\limits_{k \in {\mathcal{u}}_{n}^{I}}{h_{imn}^{H}w_{kn}s_{kn}^{I}}}} + \overset{\overset{{interference}\mspace{14mu}{induced}\mspace{14mu}{by}\mspace{14mu}{energy}\mspace{14mu}{signals}}{︷}}{\sum\limits_{n \in \mathcal{M}}{\sum\limits_{j \in {\mathcal{u}}_{n}^{E}}{h_{imn}^{H}v_{jn}s_{jn}^{E}}}} + n_{im}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack \\{y_{jm}^{E} = {{\sum\limits_{n \in \mathcal{M}}{\sum\limits_{k \in {\mathcal{u}}_{n}^{E}}{g_{jmn}^{H}w_{kn}s_{kn}^{I}}}} + {\sum\limits_{n \in \mathcal{M}}{\sum\limits_{l \in {\mathcal{u}}_{n}^{E}}{g_{jmn}v_{\ln}s_{\ln}^{E}}}} + n_{jm}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Here, h_(imn) may mean a channel between the n^(th) (here, n is anatural number) base station and the i^(th) information user of them^(th) cell, g_(jmn) may mean a channel between the n^(th) (here, n is anatural number) base station and the j^(th) energy user of the m^(th)cell, n_(im) ^(I) may mean a noise of the i^(th) information user of them^(th) cell, and n_(jm) ^(E) y may mean a noise of the j^(th) energyuser of the m^(th) cell.

The noise deriving unit 130 may extract a noise from the receptionsignal of the i^(th) (here, i is a natural number) information useramong the plurality of information users included in the m^(th) (here, mis a natural number) cell, and derive a noise power (σ_(im) ²) from theextracted noise.

The noise deriving unit 130 may derive a SINR (SINR_(im), Signal toInterference plus Noise Ratio) of the i^(th) (here, i is a naturalnumber) information user of each m^(th) (here, m is a natural number)cell by applying the derived noise power to [Equation 4] below.

$\begin{matrix}{{SINR}_{im} = \frac{\left( {{h_{imm}^{H}w_{im}}}^{2} \right)}{\begin{matrix}{{\sum\limits_{k \in {{\mathcal{u}}_{m}^{I}\backslash{\{ i\}}}}{{h_{imm}^{H}w_{km}}}^{2}} + {\sum\limits_{n \in {\mathcal{M}\backslash{\{ m\}}}}{\sum\limits_{k \in {\mathcal{u}}_{n}^{I}}{{h_{imn}^{H}w_{kn}}}^{2}}} +} \\{{\sum\limits_{n \in {\mathcal{M}\backslash{\{ m\}}}}{\sum\limits_{j \in {\mathcal{u}}_{n}^{I}}{{h_{imn}^{H}v_{jn}}}^{2}}} + \sigma_{im}^{2}}\end{matrix}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

The harvested power deriving unit 150 may derive a total harvested power(E_(jm)) by using a linear harvested power (E_(jm) ^(Linear)) and anon-linear harvested power (E_(jm) ^(Non-linear)) of the j^(th) (here, jis a natural number) energy user included in the m^(th) (here, m is anatural number) cell.

The harvested power deriving unit 150 may derive the linear harvestedpower (E_(jm) ^(Linear)) by using [Equation 5] below.

$\begin{matrix}{E_{jm}^{Linear} = {\eta_{jm}P_{jm}^{EH}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Here, η_(jm) is a positive number between 0 and 1 to represent theefficiency of converting the received RF signal into a power and maymean a power conversion efficiency of the j^(th) energy user of them^(th) cell, and P_(jm) ^(EH) may mean a power of the reception signalof the j^(th) energy user of the m^(th) cell.

The harvested power deriving unit 150 may derive the non-linearharvested power (E_(jm) ^(Non-linear)) by using [Equation 6] below.

$\begin{matrix}{E_{jm}^{Nonlinear} = \frac{\frac{M_{jm}}{1 + {\exp\left( {- {a_{jm}\left( {P_{jm}^{EH} - b_{jm}} \right)}} \right)}} - {M_{jm}\Omega_{jm}}}{1 - \Omega_{jm}}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

Here, M_(jm) may mean a maximum harvested power of the j^(th) energyuser of the m^(th) cell.

In addition, a_(jm) may mean a charging rate of the j^(th) energy userof the m^(th) cell, b_(jm) may mean a sensitivity of the j^(th) energyuser of the m^(th) cell, and Ω_(jm) may be calculated by [Equation 7]using a_(jm) and b_(jm).

$\begin{matrix}{\Omega_{jm}\frac{1}{1 + {\exp\left( {a_{jm}b_{jm}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

P_(jm) ^(EH) that is the power of the reception signal of the j^(th)energy user of the m^(th) cell receiving the energy may be derived using[Equation 8] below.

$\begin{matrix}{{P_{jm}^{EH}{{\mathbb{E}}\left\lbrack {y_{jm}^{E}}^{2} \right\rbrack}} = {\sum\limits_{n \in \mathcal{M}}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{g_{jmn}^{H}w_{kn}}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{g_{jmn}^{H}v_{l\; n}}}^{2}}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

The forming unit 170 may perform beamforming that maximizes energyharvesting efficiency (EHE) by [Equation 9] by using the power(P_(total)) of the transmission signal derived by the signal derivingunit 110 and a total harvested power of the plurality of energy usersderived from the total harvested power (E_(jm)) derived by the harvestedpower deriving unit 150.

$\begin{matrix}{{\max\mspace{14mu}{EHE}} = {\frac{{{total}\mspace{14mu}{harvested}\mspace{14mu}{power}\mspace{14mu}{of}\mspace{14mu}{energy}\mspace{14mu}{users}}\;}{{{transmission}\mspace{14mu}{power}\mspace{14mu}{at}\mspace{14mu}{base}\mspace{14mu}{station}}\;} = \frac{\sum_{m \in M}{\sum_{j \in u_{m}^{E}}E_{jm}}}{P_{total}}}} & \left\lbrack {{Equation}\mspace{20mu} 9} \right\rbrack\end{matrix}$

Here, the power (P_(total)) of the transmission signal may be derivedusing [Equation 10] below.

$\begin{matrix}{P_{total} = {\Sigma_{m \in}\left( {{\Sigma_{i \in \mathcal{U}_{m}^{\mathcal{I}}}{w_{im}}^{2}} + {\Sigma_{j \in \mathcal{U}_{m}^{E}}{v_{jm}}^{2}} + P_{C,m}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

That is, maximum energy-efficient beamforming of the beamformingapparatus 100 according to an embodiment of the present disclosure maymean the total harvested power of the energy users with respect to thetransmission power at the base station.

FIG. 2 is a block diagram concretely showing a harvested power derivingunit of FIG. 1.

The harvested power deriving unit 150 of the beamforming apparatus 100proposed by the present disclosure may include a first deriving unit151, a second deriving unit 155, and a coupling unit 159.

The first deriving unit 151 may derive a linear harvested power (E_(jm)^(Linear)) by applying the j^(th) (here, j is a natural number) energyuser of the m^(th) (here, m is a natural number) cell receiving theenergy signal to a linear model such as [Equation 5] described above.

The first deriving unit 151 may derive the linear harvested power(E_(jm) ^(Linear)) by applying to a linear model using a centralizedalgorithm.

First, a maximum value of the linear harvested power (E_(jm) ^(Linear))derived by applying to a linear model according to [Equation 5]described above by using a centralized algorithm may be calculated using[Equation 11] below.

$\begin{matrix}{{\max\limits_{{\{{{\overset{\_}{w}}_{k\; m},{\overset{\_}{v}}_{l\; m}}\}},\alpha}\mspace{11mu}{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}\;{{\overset{\_}{w}}_{k\; m}^{H}G_{m}{\overset{\_}{w}}_{k\; m}}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{\overset{\_}{v}}_{l\; m}^{H}G_{m}{\overset{\_}{v}}_{l\; m}}}} \right)}}\mspace{79mu}{{{s.t.\mspace{14mu}{\overset{\_}{SINR}}_{i\; m}} \geq \gamma_{im}},{\forall{i \in \mathcal{U}_{m}^{I}}},{\forall{m \in \mathcal{M}}},\mspace{79mu}{{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{\overset{\_}{w}}_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{\overset{\_}{v}}_{l\; m}}^{2}}} \leq {\alpha\; P_{T,m}}},{\forall{m \in \mathcal{M}}},\mspace{79mu}{{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{\overset{\_}{w}}_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{\overset{\_}{v}}_{l\; m}}^{2}}} \leq {\alpha\; P_{C,m}}} \right)} = 1}}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

Here, G_(m) may be defined as G_(m)

Σ_(n∈M)Σ_(j∈u) _(n) _(E) η_(jn)g_(jnm)g_(jnm) ^(H), ∀m∈M, γ_(im).

In addition, w_(km) may mean √{square root over (α)}w_(km), v_(im) maymean √{square root over (α)}v_(im), it may mean ∀l∈u_(m) ^(I), ∀m∈M, andSINR_(im) may be defined by [Equation 12] below.

$\begin{matrix}{\;{{\overset{\_}{SINR}}_{i\; m} = \frac{{{h_{i\; m\; i\; n}^{H}{\overset{\_}{w}}_{i\; m}}}^{2}}{\begin{matrix}{{\sum\limits_{k \in {\mathcal{U}_{m}^{I}\backslash{\{ i\}}}}{{h_{i\; m\; i\; n}^{H}{\overset{\_}{w}}_{i\; m}}}^{2}} + {\sum\limits_{m \in {\mathcal{M}\backslash{\{ m\}}}}^{\;}{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{h_{i\; m\; i\; n}^{H}{\overset{\_}{w}}_{kn}}}^{2}}} +} \\{{\sum\limits_{m \in \mathcal{M}}^{\;}{\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{h_{i\; m\; i\; n}^{H}{\overset{\_}{v}}_{i\; n}}}^{2}}} + {\sigma_{i\; m}^{2}\alpha}}\end{matrix}}}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

The final equation obtained from [Equation 11] may mean [Equation 13].

$\begin{matrix}{{{\max\limits_{{\{{{\overset{\_}{w}}_{k\; m},{\overset{\_}{v}}_{l\; m}}\}},\alpha}\;{f_{1}\left( {\left\{ {{\overset{\_}{w}}_{k\; m},{\overset{\_}{v}}_{l\; m}} \right\},\alpha} \right)}}\overset{\Delta}{=}\frac{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}\;{{\overset{\_}{w}}_{k\; m}^{H}G_{m}{\overset{\_}{w}}_{k\; m}}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{\overset{\_}{v}}_{l\; m}^{H}G_{m}{\overset{\_}{v}}_{l\; m}}}} \right)}{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{\overset{\_}{w}}_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{\overset{\_}{v}}_{l\; m}}^{2}} + {\alpha\; P_{C,m}}} \right)}}\mspace{79mu}{{{s.t.\mspace{14mu}{\overset{\_}{SINR}}_{i\; m}} \geq \gamma_{im}},{\forall{i \in \mathcal{U}_{m}^{I}}},{\forall{m \in \mathcal{M}}},\mspace{79mu}{{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{\overset{\_}{w}}_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{\overset{\_}{v}}_{l\; m}}^{2}}} \leq {\alpha\; P_{T,m}}},{\forall{m \in \mathcal{M}}}}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

Here, if rank (w_(km) ) is smaller than or equal to 1 and rank (v_(jm) )is smaller than or equal to 1, [Equation 11] may be expressed as[Equation 14] below.

$\begin{matrix}{{\max\limits_{{\{{{{\overset{\_}{w}}_{k\; m} \succcurlyeq 0},{{\overset{\_}{v}}_{l\; m} \succcurlyeq 0}}\}},\alpha}\;{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{tr}\left( {G_{m}{\overset{\_}{W}}_{k\; m}} \right)}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{tr}\left( {G_{m}{\overset{\_}{V}}_{l\; m}} \right)}}} \right)}}\mspace{79mu}{{{s.t.\mspace{14mu}{\overset{\_}{SINR}}_{i\; m}^{SDR}} \geq \gamma_{im}},{\forall{i \in \mathcal{U}_{m}^{I}}},{\forall{m \in \mathcal{M}}},\mspace{76mu}{{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{tr}\left( {\overset{\_}{W}}_{k\; m} \right)}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{tr}\left( {\overset{\_}{V}}_{l\; m} \right)}}} \leq {\alpha\; P_{T,m}}},{\forall{m \in \mathcal{M}}},\mspace{79mu}{{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{tr}\left( {\overset{\_}{W}}_{k\; m} \right)}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{tr}\left( {\overset{\_}{V}}_{l\; m} \right)}} + {\alpha\; P_{C,m}}} \right)} = 1}}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

Here, H_(imn) may be defined as h_(inm)h_(inm) ^(H), it may mean∀i∈u_(m) ^(I)∀m, n∈M, X≥0, and SINR_(im) ^(SDR) may be defined by[Equation 15] below.

$\begin{matrix}{{\overset{\_}{SINR}}_{i\; m}^{SDR} = \frac{{tr}\left( {H_{i\; m\; m}{\overset{\_}{W}}_{k\; m}} \right)}{\begin{matrix}{{\sum\limits_{k \in {\mathcal{U}_{m}^{l}\backslash{\{ i\}}}}{{tr}\left( {H_{i\; m\; m}{\overset{\_}{W}}_{k\; m}} \right)}} + {\sum\limits_{m \in {\mathcal{M}\backslash{\{ m\}}}}^{\;}{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{{tr}\left( {H_{i\; m\; m}{\overset{\_}{W}}_{k\; m}} \right)}}} +} \\{{\sum\limits_{m \in \mathcal{M}}^{\;}{\sum\limits_{l \in \mathcal{U}_{m}^{E}}{{tr}\left( {H_{i\; m\; m}{\overset{\_}{v}}_{i\; n}} \right)}}} + {\sigma_{i\; m}^{2}\alpha}}\end{matrix}}} & \left\lbrack {{Equation}\mspace{14mu} 15} \right\rbrack\end{matrix}$

The second deriving unit 155 may derive a non-linear harvested power(E_(jm) ^(Non-linear)) by applying the j^(th) (here, j is a naturalnumber) energy user of the m^(th) (here, m is a natural number) cellreceiving the energy signal to a non-linear model such as [Equation 6]described above.

The second deriving unit 155 may derive the non-linear harvested power(E_(jm) ^(Non-linear)) by applying to a non-linear model using acentralized algorithm.

First, a maximum value of the non-linear harvested power (E_(jm)^(Non-linear)) derived by applying to a non-linear model according to[Equation 6] described above by using a centralized algorithm may becalculated using [Equation 16] below.

$\begin{matrix}{{\max\limits_{\{{w_{k\; m},v_{l\; m}}\}}\mspace{11mu}\frac{\begin{matrix}{\sum\limits_{m \in \mathcal{M}}^{\;}{\sum\limits_{l \in \mathcal{U}_{m}^{E}}\frac{M_{l\; m}}{1 - \Omega_{l\; m}}}} \\\left( {\frac{1}{1 + {\exp\left( {- {a_{im}\left( {P_{l\; m}^{ER} - b_{im}} \right)}} \right)}} - \Omega_{l\; m}} \right)\end{matrix}}{\sum\limits_{m \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{w_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{v_{l\; m}}^{2}} + P_{C,m}} \right)}}{{{s.t.\mspace{14mu}{SINR}_{im}} \geq \gamma_{im}},{\forall{i \in \mathcal{U}_{m}^{I}}},{\forall{m \in \mathcal{M}}},{{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{w_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{v_{l\; m}}^{2}}} \leq P_{T,m}},{\forall{m \in \mathcal{M}}},}} & \left\lbrack {{Equation}\mspace{14mu} 16} \right\rbrack\end{matrix}$

[Equation 16] may be expressed as [Equation 17] and [Equation 18] below,and the non-linear harvested power (E_(jm) ^(Non-linear)) may be derivedusing [Equation 19] therefrom.

$\begin{matrix}{{\hat{q}}^{*} = {\frac{U\left( \left\{ {w_{k\; m}^{*},v_{l\; m}^{*}} \right\} \right)}{U_{TP}\left( \left\{ {w_{k\; m}^{*},v_{l\; m}^{*}} \right\} \right)} = {\max\limits_{{\{{w_{k\; m},v_{l\; m}}\}} \in \mathcal{F}}\;\frac{U\left( \left\{ {w_{k\; m},v_{l\; m}} \right\} \right)}{U_{TP}\left( \left\{ {w_{k\; m},v_{l\; m}} \right\} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 17} \right\rbrack\end{matrix}$

Here, like [Equation 16], the conditions for a numerator and adenominator may be defined as U({w_(km), v_(im)})>0, U_(TP) ({w_(km),v_(im)})≥0, respectively.

$\begin{matrix}{{T\left( {\hat{q}}^{*} \right)} = {{{\max\limits_{{\{{w_{km},v_{lm}}\}} \in}{U\left( \left\{ {w_{km},v_{lm}} \right\} \right)}} - {{\hat{q}}^{*}{U_{TP}\left( \left\{ {w_{km},v_{lm}} \right\} \right)}}} = 0}} & \left\lbrack {{Equation}\mspace{14mu} 18} \right\rbrack\end{matrix}$

From the above, the maximum value f EHE{circumflex over (q)}* may meanwhen T({circumflex over (q)}*) is 0.

$\begin{matrix}{{{\max\limits_{\{{w_{k\; m},v_{l\; m}}\}}\;{U\left( \left\{ {w_{k\; m},v_{l\; m}} \right\} \right)}} - {\hat{q}{U_{TP}\left( \left\{ {w_{k\; m},v_{l\; m}} \right\} \right)}}}{{s.t.\mspace{14mu}{SINR}_{i\; m}} \geq \gamma_{im}},{\forall{i \in \mathcal{U}_{m}^{I}}},{\forall{m \in \mathcal{M}}},{{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{w_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{v_{l\; m}}^{2}}} \leq P_{T,m}},{\forall{m \in \mathcal{M}}}} & \left\lbrack {{Equation}\mspace{14mu} 19} \right\rbrack\end{matrix}$

[Equation 19] may be expressed as [Equation 20] below.

$\begin{matrix}{\mspace{79mu}{{{\max\limits_{\{{w_{k\; m},v_{l\; m},\rho_{l\; m}}\}}\mspace{11mu}{\sum\limits_{m \in \mathcal{M}}^{\;}{\sum\limits_{l \in \mathcal{U}_{m}^{E}}{\hat{U}\left( \rho_{l\; m} \right)}}}} - {\hat{q}{U_{TP}\left( \left\{ {w_{k\; m},v_{l\; m}} \right\} \right)}}}{{{s.t.\mspace{11mu}{\sum\limits_{n \in \mathcal{M}}^{\;}\left( {{\sum\limits_{k \in \mathcal{U}_{n}^{I}}{{g_{jmn}^{H}w_{kn}}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{n}^{E}}{{g_{jmn}^{H}v_{l\; n}}}^{2}}} \right)}} \geq \rho_{jm}},{\forall{j \in \mathcal{U}_{m}^{E}}},{\forall{m \in \mathcal{M}}}}\mspace{79mu}{{{SINR}_{im} \geq \gamma_{im}},{\forall{i \in \mathcal{U}_{m}^{I}}},{\forall{m \in \mathcal{M}}},\mspace{79mu}{{{\sum\limits_{k \in \mathcal{U}_{m}^{I}}{w_{k\; m}}^{2}} + {\sum\limits_{l \in \mathcal{U}_{m}^{E}}{v_{l\; m}}^{2}}} \leq P_{T,m}},{\forall{m \in \mathcal{M}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 20} \right\rbrack\end{matrix}$

$\overset{\_}{U}\left( \rho_{lm} \right)\;\frac{M_{lm}}{1 - \Omega_{lm}}{\left( {\frac{1}{1 + {\exp\left( {- {a_{lm}\left( {\rho_{lm} - b_{lm}} \right)}} \right)}} - \Omega_{1m}} \right).}$

Here, it may mean

From the above, [Equation 21] may be calculated.

⁢max { w k ⁢ ⁢ m , v l ⁢ ⁢ m , ρ l ⁢ ⁢ m } ⁢ ⁢ ∑ m ∈ ℳ ⁢ ∑ l ∈ 𝒰 m E ⁢ U LB ( l ) ^⁡( ρ l ⁢ ⁢ m ) - q ^ ⁢ U TP ⁡ ( { w k ⁢ ⁢ m , v l ⁢ ⁢ m } ) ⁢ ⁢ ⁢ s . t . ⁢ im SDR ≥γ im , ∀ i ∈ 𝒰 m I , ∀ m ∈ ℳ , ⁢ ⁢ ∑ k ∈ 𝒰 m I ⁢ tr ⁡ ( W k ⁢ ⁢ m ) + ∑ l ∈ 𝒰m E ⁢ ( V l ⁢ ⁢ m ) ≤ P T , m , ∀ m ∈ ℳ , ⁢ ∑ n ∈ ℳ ⁢ ( ∑ k ∈ 𝒰 m I ⁢ tr ⁡ ( G^ jmn ⁢ W kn ) + ∑ l ∈ 𝒰 m E ⁢ tr ⁡ ( G ^ jmn ⁢ V i ⁢ ⁢ n ) ) ≥ ρ jm , ∀ j ∈ 𝒰m E , ∀ m ∈ ℳ [ Equation ⁢ ⁢ 21 ]

Here, it may mean w_(km)

w_(km)w_(km) ^(H), it may mean v_(im)

v_(im)v_(im) ^(H), it may mean U_(TP)({w_(km), v_(im)})

Σ_(m∈M) (Σ_(k∈u) _(m) _(I) tr(w_(km))+Σ_(l∈u) _(m) _(E)tr(v_(im))+P_(C,m)), it may mean Ĝ_(jm)

g_(imn)g_(jmn) ^(H), ∀l, j∈u_(m) ^(E), ∀m, n∈M, and

_(im) ^(SDR) may be calculated using [Equation 22] below.

i ⁢ ⁢ m SDR = tr ⁡ ( H imm ⁢ W im ) ∑ k ∈ 𝒰 m I ⁢ tr ⁢ ( H imm ⁢ W k ⁢ ⁢ m ) + ∑n ∈ ℳ ⁢ \ ⁢ { m } ⁢ ∑ k ∈ 𝒰 n I ⁢ tr ⁢ ( H imn ⁢ W kn ) + ∑ n ∈ ℳ ⁢ ∑ l ∈ 𝒰 m E⁢tr ⁡ ( H imn ⁢ V i ⁢ ⁢ n ) + σ im 2 [ Equation ⁢ ⁢ 22 ]

From the above, a centralized algorithm may be arranged as in [Table 1]below.

TABLE 1 Algorithm 1: Centralized algorithm for the non-linear EH modell: Set {circumflex over (q)} = 0. 2: Initialize t = 0 and {ρ_(lm)^((t))} = 0. 3: Let t ← t + 1. Solve the problem [

 22] for a given {circumflex over (q)}, and obtain {ρ_(lm) ^((t))}. 4:If {ρ_(lm) ^((t))} converge, return {W_(km) ^(*)} and go to step 5.Otherwise, go back to step 3. 5: Compute {w_(km) ^(*)} by EVD of {W_(km)^(*)} and set {v_(lm) ^(*)} = 0. 6: If U ({w_(km) ^(*), v_(lm) ^(*)})

 {circumflex over (q)}U_(TP) ({w_(km) ^(*), v_(lm) ^(*)}) converges,return {w_(km)*, v_(lm)*} and then stop. Otherwise, update$\hat{q} = \frac{U\left( \left\{ {w_{km}^{*},v_{lm}^{*}} \right\} \right)}{U_{TP}\left( \left\{ {w_{km}^{*},v_{lm}^{*}} \right\} \right)}$and go back to step 2.

indicates data missing or illegible when filed

After setting {circumflex over (q)}=0 and initializing as t=0, {ρ_(im)^((t))}=0, [Equation 21] may be solved by increasing the t value by ‘1’,and if {ρ_(im) ^((t))} converges, {W*_(km)} may be solved by performingthe fifth step, but otherwise, the third step may be performed again.

After performing the fifth step, if U({w*_(km), v*_(im)})−{circumflexover (q)}U_(TP)({w*_(km), v*_(im)}) converges, solving the correspondingequation may be stopped, but if not, the process may return to thesecond step to update

$\overset{\hat{}}{q} = {\frac{U\left( \left\{ {w_{k\; m}^{*},v_{l\; m}^{*}} \right\} \right)}{U_{TP}\left( \left\{ {w_{k\; m}^{*},v_{l\; m}^{*}} \right\} \right)}.}$

The coupling unit 159 may derive a total harvested power (E_(jm)) byusing the linear harvested power (E_(jm) ^(Linear)) derived by the firstderiving unit 151 and the non-linear harvested power (E_(jm)^(Non-linear)) derived by the second deriving unit.

Hereinafter, a beamforming method in a simultaneous wireless informationand power transfer system will be described in detail with reference toFIGS. 3 and 4.

FIG. 3 is a flowchart for schematically illustrating a beamformingmethod in a simultaneous wireless information and power transfer systemaccording to an embodiment of the present disclosure.

A transmission signal transmitted to a plurality of information usersand a plurality of energy users from a base station (BS) having an N_(T)(here, N_(T) is a natural number) number of antennas included in eachcell may be derived (S1100).

Here, an m (here, m is a natural number) number of cells may beprovided, and the cell may include one base station having an N_(T)(here, N_(T) is a natural number) number of antennas, a plurality ofinformation users, and a plurality of energy users.

The base station may simultaneously transmit information and power tothe plurality of information users and the plurality of energy usershaving a single antenna by using the N_(T) (here, N_(T) is a naturalnumber) number of antennas.

The information users and the energy users receiving the informationsignal and the energy signal from the m^(th) (here, m is a naturalnumber) base station may derive reception signals (y_(im) ^(I), y_(jm)^(E)), received from each antenna.

The noise of the i^(th) (here, i is a natural number) information useramong the plurality of information users receiving the informationsignal from the m^(th) (here, m is a natural number) base station may beextracted from the derived reception signal (y_(im) ^(I)).

A noise power (σ_(im) ²) for the reception signal of the i^(th)information user of the m^(th) cell may be derived from the extractednoise, and a SINR (SINR_(im), Signal to Interference plus Noise Ratio)of the i^(th) information user of the m^(th) cell may be derived usingthe derived noise power (σ_(im) ²) (S1300).

Meanwhile, a harvested power may be derived using the reception signal(y_(jm) ^(E)) of the j^(th) (here, j is a natural number) energy useramong the plurality of energy users receiving the energy signal from them^(th) (here, m is a natural number) base station (S1500).

Here, the harvested power of the energy user may be derived using thelinear harvested power (E_(jm) ^(Linear)) and the non-linear harvestedpower (E_(jm) ^(Non-linear)) of the j^(th) (here, j is a natural number)energy user of the m^(th) (here, m is a natural number) cell.

Energy-efficient beamforming (EHE, Energy Harvesting Efficiency) may beperformed using the power (P_(total)) of the transmission signals of thebase stations having an N_(T) (here, N_(T) is a natural number) numberof antennas and the total harvested power (E_(jm)) of the energy users(S1700).

That is, maximum energy-efficient beamforming of the beamformingapparatus 100 according to an embodiment of the present disclosure maymean the total harvested power of the energy users with respect to thetransmission power at the base station.

FIG. 4 is a flowchart for concretely illustrating a process of derivinga harvested power of FIG. 3.

Among the plurality of energy users of the m^(th) (here, m is a naturalnumber) cell receiving the energy signal, the j^(th) (here, j is anatural number) energy user may be applied to a linear model (S1310).

The linear harvested power (E_(jm) ^(Linear)) may be derived using thepower (P_(jm) ^(EH)) and the power conversion efficiency (η_(jm)) of thereception signal received by the j^(th) energy user of the m^(th) cellfrom the antenna (S1330).

Here, the power conversion efficiency (η_(jm)) may mean a positivenumber between 0 and 1 to represent the efficiency of converting the RFsignal received by the j^(th) energy user of the m^(th) cell from theantenna into a power.

After deriving the linear harvested power (E_(jm) ^(linear)), among theplurality of energy users of the m^(th) (here, m is a natural number)cell receiving the energy signal, the j^(th) (here, j is a naturalnumber) energy user may be applied to a non-linear model (S1350).

The non-linear harvested power (E_(jm) ^(Non-linear)) may be derivedusing the maximum harvested power (M_(jm)), the charging rate (a_(jm))and the sensitivity (b_(jm)) of the j^(th) energy user of the m^(th)cell (S1370).

The total harvested power (E_(jm)) for the j^(th) energy user of them^(th) cell may be derived using the derived linear harvested power andthe derived non-linear harvested power (E_(jm) ^(Non-linear)) (S1390).

Hereinafter, an embodiment of the beamforming method in a simultaneouswireless information and power transfer system proposed by the presentdisclosure will be described with reference to FIGS. 5 to 7.

FIG. 5 is an exemplary diagram showing a simultaneous wirelessinformation and power transfer system 10 to which the beamformingapparatus in a simultaneous wireless information and power transfersystem 10 proposed in the present disclosure is applied.

The present disclosure is directed to a beamforming apparatus 100considering a multi-user simultaneous wireless information and powertransfer system 10, and the base station having an N_(T) (here, N_(T) isa natural number) number of antennas may transmit information and energysimultaneously to a plurality of information users and a plurality ofenergy users having a single antenna.

That is, the base station including the N_(T) (here, N_(T) is a naturalnumber) number of antennas may be provided as an m (here, m is a naturalnumber) number of base stations 50 a, . . . , 50 m, and each basestation 50 a, . . . , 50 m may transmit an information signal or anenergy signal to a plurality of information users 70 a, . . . , 70 i orenergy users 30 a, . . . , 30 j included in the range where aninformation signal or an energy signal may be transmitted.

For example, one base station 50 a may transmit an information signal toan i (here, i is a natural number) number of information users 70 a ₁, .. . , 70 i ₁ included in a group of information users (U₁ ^(I) ID user)included in the range where an information signal may be transmitted.

One base station 50 a may transmit an energy signal to a j (here, j is anatural number) number of energy users 30 a ₁, . . . , 30 j ₁ includedin a group of energy users (U₁ ^(E) EH user) included in the range wherean energy signal may be transmitted.

In addition, the present disclosure may maximize the performance of theenergy user in consideration of the transmission power while satisfyingthe quality of service (QoS) of the information user, and may alsoderive a harvested power in consideration of not only a linear model butalso a non-linear model.

The result of applying the reception signal of the energy user to alinear model and a non-linear model in order to derive the harvestedpower will be described with reference to FIGS. 6 and 7.

FIGS. 6 and 7 are diagrams showing results obtained by applying thebeamforming method in the simultaneous wireless information and powertransfer system proposed in the present disclosure to a linear model anda non-linear model, respectively.

Referring to FIG. 6, it may be found that the beamforming method in thesimultaneous wireless information and power transfer system 10 proposedby the present disclosure is performed similar to max-HE (a techniquefor maximizing only a numerator of EHE in [Equation 9]).

However, as the transmission power increases, it may be found that thetechnique proposed in the present disclosure has better performance thanthe max-EH technique.

In addition, referring to FIG. 7, it may be found that the beamformingmethod in the simultaneous wireless information and power transfersystem 10 proposed by the present disclosure is not performed similar tothe beamforming maximum value (max-HE).

The non-linear harvested power (E_(jm) ^(Non-linear)) derived by thebeamforming method proposed by the present disclosure is generated as avalue greater than the max-HE method because when transmitting the powerof the transmission signal of the antenna, the magnitude of powerconsumed by the max-HE technique is greater than the magnitude of powerconsumed by the technique proposed in the present disclosure.

As described above, the beamforming method of the present disclosureimproves the effect of minimizing the transmission power of the basestation and maximizing the harvested power of the energy users, whilesatisfying the QoS (Quality of Service) and transmission powerlimitation of the information users.

The beamforming method in a simultaneous wireless information and powertransfer system as described above may be implemented as an applicationor in the form of program commands that may be executed through variouscomputer components, and may be recorded in a computer-readablerecording medium. The computer-readable recording medium may include aprogram command, a data file, a data structure, or the like alone or incombination.

The program commands recorded in the computer-readable recording mediummay be specially designed and constructed for the present disclosure andmay be already known to and usable by those skilled in the computersoftware field.

Examples of the computer-readable recording medium include magneticmedia such as hard disks, floppy disks and magnetic tapes, opticalrecording media such as CD-ROMs and DVDs, magnetic-optical media such asfloptical disks, and hardware devices specially configured to store andexecute program commands such as ROM, RAM and flash memories.

Examples of the program command include not only machine language codesproduced by a compiler but also high-level language codes that may beexecuted by a computer using an interpreter or the like. The hardwaredevice may be configured to operate as one or more software modules toperform the processing according to the present disclosure, or viceversa.

Although the present disclosure has been described with reference toembodiments, it would be understood that various modifications andchanges can be made by those skilled in the art from the presentdisclosure without departing from the idea and scope defined in theappended claims.

REFERENCE SIGNS

-   -   10: simultaneous wireless information and power transfer system    -   100: beamforming apparatus in a simultaneous wireless        information and power transfer system    -   110: signal deriving unit    -   130: noise deriving unit    -   150: harvested power deriving unit    -   151: first deriving unit    -   155: second deriving unit    -   159: coupling unit    -   170: forming unit    -   30 a, . . . , 30 j: energy user    -   50 a, . . . , 50 m: antenna    -   70 a, . . . , 70 i: information user

1. A beamforming method in a simultaneous wireless information and powertransfer system, comprising: deriving a transmission signal transmittedto a plurality of information users and a plurality of energy users froma base station having an N_(T) (here, N_(T) is a natural number) numberof antennas included in each cell; deriving a SINR (Signal toInterference plus Noise Ratio) of an i^(th) (here, i is a naturalnumber) information user by using a noise power of the i^(th) (here, iis a natural number) information user included in a m^(th) (here, m is anatural number) cell; deriving a harvested power of a j^(th) (here, j isa natural number) energy user included in the m^(th) (here, m is anatural number) cell; and performing beamforming by using a transmissionsignal power at the base station and a total harvested power of theplurality of energy users receiving a transmission signal from the basestation.
 2. The beamforming method in a simultaneous wirelessinformation and power transfer system according to claim 1, wherein saidderiving of a harvested power includes: deriving a linear harvestedpower by applying the j^(th) (here, j is a natural number) energy userof the m^(th) (here, m is a natural number) cell to a linear model,deriving a non-linear harvested power by applying the j^(th) (here, j isa natural number) energy user of the m^(th) (here, m is a naturalnumber) cell to a non-linear model, and deriving a harvested power forthe j^(th) (here, j is a natural number) energy user of the m^(th)(here, m is a natural number) cell by using the derived linear andnon-linear harvested powers.
 3. The beamforming method in a simultaneouswireless information and power transfer system according to claim 2,wherein said deriving of a linear harvested power includes: deriving thelinear harvested power by using a reception signal power (P_(jm) ^(E))and a power conversion efficiency (η_(jm)) of the j^(th) (here, j is anatural number) energy user of the m^(th) (here, m is a natural number)cell.
 4. The beamforming method in a simultaneous wireless informationand power transfer system according to claim 2, wherein said deriving ofa non-linear harvested power includes: deriving the non-linear harvestedpower by using a maximum harvested power (M_(jm)), a charging rate(a_(jm)) and a sensitivity (b_(jm)) of the j^(th) (here, j is a naturalnumber) energy user of the m^(th) (here, m is a natural number) cell,which are parameters of the non-linear model.
 5. The beamforming methodin a simultaneous wireless information and power transfer systemaccording to claim 1, wherein said performing of beamforming includes:non-linearly optimizing the transmission signal power of the basestation and the total harvested power of the energy users based on QoS(Quality of Service) of the information users.
 6. A computer-readablerecording medium, in which a computer program for performing thebeamforming method in a simultaneous wireless information and powertransfer system according to claim 1 is recorded.
 7. A beamformingapparatus in a simultaneous wireless information and power transfersystem, comprising: a signal deriving unit configured to derive atransmission signal transmitted to a plurality of information users anda plurality of energy users from a base station having an N_(T) (here,N_(T) is a natural number) number of antennas included in each cell; anoise deriving unit configured to derive a SINR of an i^(th) (here, i isa natural number) information user by using a noise power of the i^(th)(here, i is a natural number) information user included in a m^(th)(here, m is a natural number) cell; a harvested power deriving unitconfigured to derive a harvested power of a j^(th) (here, j is a naturalnumber) energy user included in the m^(th) (here, m is a natural number)cell; and a forming unit configured to perform beamforming by using atransmission signal power derived by the signal deriving unit and atotal harvested power of the plurality of energy users derived from theharvested power derived by the harvested power deriving unit.
 8. Thebeamforming apparatus in a simultaneous wireless information and powertransfer system according to claim 7, wherein the harvested powerderiving unit includes: a first deriving unit configured to derive alinear harvested power by applying the j^(th) (here, j is a naturalnumber) energy user of the m^(th) (here, m is a natural number) cell toa linear model; a second deriving unit configured to derive a non-linearharvested power by applying the j^(th) (here, j is a natural number)energy user of the m^(th) (here, m is a natural number) cell to anon-linear model; and a coupling unit configured to derive a harvestedpower for the j^(th) (here, j is a natural number) energy user of them^(th) (here, m is a natural number) cell by using the derived linearand non-linear harvested powers.
 9. The beamforming apparatus in asimultaneous wireless information and power transfer system according toclaim 8, wherein the first deriving unit is configured to derive thelinear harvested power by using a reception signal power (P_(jm) ^(E))and a power conversion efficiency (η_(jm)) of the j^(th) (here, j is anatural number) energy user of the mm (here, m is a natural number)cell.
 10. The beamforming apparatus in a simultaneous wirelessinformation and power transfer system according to claim 8, wherein thesecond deriving unit is configured to derive the non-linear harvestedpower by using a maximum harvested power (M_(jm)), a charging rate(a_(jm)) and a sensitivity (b_(jm)) of the j^(th) (here, j is a naturalnumber) energy user of the m^(th) (here, m is a natural number) cell,which are parameters of the non-linear model.
 11. The beamformingapparatus in a simultaneous wireless information and power transfersystem according to claim 7, wherein the forming unit is configured tonon-linearly optimize the transmission signal power of the base stationand the total harvested power of the energy users based on QoS (Qualityof Service) of the information users.